47re performance ?'s

S

sstockton

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May 17, 2007
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What are the differences in the intermediate band apply levers? It seems like different companies use different ratio's and I'm wondering why, and what the differences in the behaviors of the trans will be as a result of switching them.

stock is 3.8:1,
HTS lists 4.2:1
My DTT has a 4.4:1,
Sun coast sells 5:1,
Dunrite recommends a 3.8:1

What can be gained by switching the apply lever? Also, if the apply lever ratio is changed, do any adjustments need to be made to band tension to keep it from being too tight or too loose?

Next question:
I've heard that a potentiometer can be used as an adjustable lock up switch. However, I don't know how reputable the source was, and didn't hear anything about how to do it. I have some ideas in my head, but it would be easier if someone had already done it. Also, if this can be done, will it automatically unlock the converter as well, so you don't have to worry/deal with unlocking it when coming to a stop. I'm not sure what the PCM signals to the lock up solenoid are, if its an increasing voltage, decreasing voltage, on/off etc... Thanks,
Sean
 
I would imagine they recommend a lever according to the Valvebody modifications they have done, which will effect shift "feel". The higher the ratio number, the more pressure applied to the band. I think a stock 48RE is a 4.8, probably cheaper if you can score one.
 
48re is a 5:1 ratio IIRC. I was just curious if it would make a more firm shift. Or increase the speed of the shift, because the servo doesn't have to travel as far to engage the band.
Sean
 
It should make a firmer shift, but a quicker shift based on servo travel will depend on band adjustment/clearence.4.8-5.1 is definately better IMO.
 
Increasing the apply lever ratio will increase the leverage/holding power on the intermediate band. They also can lead to 2-3 shift overlap/binding. Timing is critical since both the intermediate band and direct clutch act on the same drum.

That said, most people that I have talked to about apply lever ratio and its effects on an automatic valve body transmission have told me to stay in the low 4s for ratio. The hemi cars from the late '60s/early '70s used a 5:1 lever but they also used a different direct drum and intermediate band as well. I believe the drum had additional springs in it to help control shift timing to avoid shift overlap. I'm not sure what the 48re uses for an apply lever or direct drum at this point since I haven't gotten to rebuild one yet.

Also, how loose or tight you adjust the band will affect shift quality and make small adjustments on shift timing.
 
Well I'll stick with the one that DTT originally put in it, since I'm still running their valvebody, and servos etc...

As for the additional springs, I know a lot of these built trans' ad 1 more spring to the direct drum, so maybe that makes a difference some too.

I'm just trying to gain a better understanding of the way everything in the trans performs and what does what/why.
Sean
 
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